In recent years, vehicles which are driven by electricity have been used. It is necessary to supply electric power to the vehicles. A power-supplying apparatus supplies electric power to a parked vehicle, for example. The power-supplying apparatus may wirelessly supply electric power to the vehicle.
For example, a technique has been proposed in which a wireless power-supplying secondary coil is provided in the bottom of a vehicle and electric power is supplied from a power-supplying primary coil below the vehicle to the vehicle. It is preferable to wirelessly supply electric power from the power-supplying primary coil to the power-supplying secondary coil with low energy loss. FIG. 6 illustrates a concept of a wireless power-supplying system. FIG. 6 is a diagram disclosed in U.S. Pat. No. 8,035,255. In addition, when electric power is wirelessly supplied from the power-supplying primary coil to the power-supplying secondary coil, it is preferable that the wireless power-supplying system be easy to use.